1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to disk drive suspensions using flexible circuit trace conductors for electrical connection of the slider head to the device electronics without the presence of undue capacitive coupling between the load beam and the trace conductors. In a particular aspect, the invention relates to disk drive suspensions having a second dielectric film between the load beam and the trace conductors that serves to reduce or eliminate electrical interference from capacitive coupling, but which is not connected to the flexible circuit at the distal portion thereof. Thus where the flexible circuit defines a flexure there is no second dielectric layer attached to the flexible circuit so that desirable mechanical properties of the suspension are retained while the electrical properties improved.
2. Related Art
Flexible circuit comprising a dielectric layer and a plurality of trace conductors such as copper traces, with or without an added metal layer, are known to be used to provide the electrical connection in a suspension. Typically, the major part of the flexible circuit electrical connector lies juxtaposed with the load beam, the flexible circuit trace conductors being disposed upon the dielectric plastic film base layer and typically covered with dielectric plastic. The flexible circuit is fixed to the load beam at spaced locations along their mutual extents, with an air gap between the load beam and the flexible circuit between the points of attachment. With reference to FIG. 3, PRIOR ART, the suspension 8 is shown to include a load beam 9, and a flexible circuit 11 spaced from the load beam across an air gap 4. The flexible circuit 11 comprises trace conductors 5 that tend to capacitively couple with the load beam 9, a dielectric layer 6 that is too thin to effectively block capacitive coupling, e.g. 0.001 inch thick, and a cover of insulating plastic 7. Increasing the thickness of the dielectric layer 6 is potentially effective to block capacitive coupling but the mechanical properties of the resulting circuit are too compromised. For example, the flexibility of the flexible circuit 11 is decreased by having a thicker dielectric layer 6 to the point that the utility of the flexible circuit to define a flexure at the distal portion of the circuit, as is desirable, is negated.